Analysis of IgG response to experimental infection with RH Toxoplasma gondii in goats

A comparative study of serological tests used in the diagnosis of Toxoplasma gondii infection in small ruminants evidenced the importance of cross-reactions for harmonizing diagnostic performance

Toxoplasma gondii is a major foodborne zoonotic pathogen that can be transmitted through the consumption of raw or undercooked meat of small ruminants, among others. Serology has been suggested as an epidemiological indicator and several tests are available nowadays. However, there is no comparative study with the most used ones. Therefore, the objective of this study was to develop and validate two in-house tests (Western blot -TgSALUVET WB- and ELISA -TgSALUVET ELISA 2.0-) and perform a comparative study including such tests and four commercial ELISA kits (IDScreen®, PrioCHECK®, Pigtype® and IDEXX). First, a specific pattern of recognition of immunodominant antigens by TgSALUVET WB was determined with serum panels of noninfected sheep and sheep infected with T. gondii or Neospora caninum. Next, TgSALUVET WB was used as a reference to preliminary validate TgSALUVET ELISA 2.0 using sera from sheep and goats naturally infected with T. gondii. Then, the abovementioned sheep serum panels were analyzed by all tests and subjected to TG-ROC analyses and agreement tests, and cross-reactivity with the anti-N. caninum IgGs was studied. All the techniques were accurate enough for the cutoff values initially suggested with all serum panels (Se and Sp ≥ 94%), except for PrioCHECK®, which showed 83% Sp. However, a cutoff readjustment improved their diagnostic performance. Additionally, cross-reactions between anti-N. caninum antibodies and T. gondii antigens were detected with all tests. Thus, a second cutoff readjustment was carried out and the use of both readjusted cutoff values is recommended to obtain comparable data and avoid false-positive results.

Toxoplasma gondii infection in goats: serological, pathological, and clinical monitoring during gestation

This study aimed to evaluate Toxoplasma gondii infection in pregnant goats. The goats were divided into two groups: group one (G1) comprised of 31 pregnant goats naturally infected with T. gondii, and group two (G2) comprised of seven uninfected pregnant goats from a flock with a history of abortion due to toxoplasmosis. Serological investigation, ultrasonography, and clinical testing were performed on all goats during gestation. Serum samples from goats and their offspring (precolostral) were collected to evaluate the vertical transmission of T. gondii. Samples from placentas and aborted fetuses were also collected for molecular and histopathological analysis. Results showed that in G1, estrus recurrence occurred in 22.6% (7/31) of the goats, embryonic death in 3.3% (1/31), and abortion in 19.4% (6/31). An increase in anti-T. gondii antibodies was observed in G1 goats at day 150 of pregnancy. T. gondii DNA was detected in 42.8% (3/7) of aborted fetuses and was associated with histopathological lesions caused by this parasite. Moreover, toxoplasmosis in field conditions caused by genotype ToxoDB #1 in pregnant goats resulted in severe reproductive loss in the flock.

Survey of selected pathogens in free-ranging pinnipeds in Uruguay

Marine mammals, regarded as sentinels of aquatic ecosystem health, are exposed to different pathogens and parasites under natural conditions. We surveyed live South American fur seals Arctocephalus australis and South American sea lions Otaria flavescens in Uruguay for Leptospira spp., canine distemper virus (CDV), Mycobacterium spp., Toxoplasma gondii, and Neospora caninum. Samples were collected from 2007 to 2013. The seroprevalence of Leptospira spp. was 37.6% positive, 50.9% negative, and 11.5% suspect for A. australis (n = 61) while for O. flavescens (n = 12) it was 67% positive, 25% negative, and 8% suspect. CDV RNA was not detected in any of the analyzed samples. Most animals tested seropositive to tuberculosis antigens by WiZo ELISA (A. australis: 29/30; O. flavescens: 20/20); reactivity varied with a novel ELISA test (antigens MPB70, MPB83, ESAT6 and MPB59). Seroprevalence against N. caninum and T. gondii was 6.7 and 13.3% positive for O. flavescens and 0 and 2.2% positive for A. australis respectively. To evaluate possible sources of infection for pinnipeds, wild rats Rattus rattus and semi-feral cats Felis catus were also tested for Leptospira spp. and T. gondii respectively. Water samples tested for Leptospira revealed saprofitic L. bioflexa. Pathogenic Leptospira were detected in the kidneys of 2 rats, and cats tested positive for T. gondii (100%). These results represent a substantial contribution to the study of the health status of wild pinnipeds in Uruguay.

Interferon-gamma expression and infectivity of Toxoplasma infected tissues in experimentally infected sheep in comparison with pigs

Livestock animals are a potential risk for transmission of toxoplasmosis to humans. Sheep and pigs still remain an important source because their meat is often eaten undercooked which has been regarded as a major route of infection in many countries. Moreover, porcine tissues are processed in many food products. In the current study, the IFN-gamma (T-helper 1 cells), IL-4 (Th2 cells) and IL-10 mRNA (Treg cells) expression by blood mononuclear cells, and the serum antibody response against Toxoplasma gondii total lysate antigen, recombinant T. gondii GRA1, rGRA7, rMIC3 and rEC2, a chimeric antigen composed of MIC2, MIC3 and SAG1, was studied in sheep the first two months after a T. gondii infection and compared with these responses in pigs. At the end of this period, the parasite distribution in heart, brain and two skeletal muscles in sheep was compared with this in pigs. Whereas the parasite distribution was similar in sheep and pigs, the antibody response differed considerably. In sheep, antibodies appeared against all tested T. gondii antigens, but mainly against rGRA7, rMIC3234307 and TLA whereas in pigs only rGRA7-specific antibodies could be demonstrated. Also, the cytokine response differed. Both in sheep and pigs an IFN-gamma response occurred which seemed to be a slightly more pronounced in sheep. In sheep, also IL-10 and IL-4 mRNA expression showed an increase, but later than IFN-gamma and with more variation. However, in pigs no such increase was seen. As concerning diagnosis, results indicate that serum antibodies against GRA7 in live sheep and pigs and heart tissue for bioassay and qPCR in slaughtered animals are the best targets to demonstrate presence of T. gondii infection.

Veterinary vaccines against toxoplasmosis

Toxoplasma gondii is a cosmopolitan protozoan parasite that infects a wide range of mammal and bird species. Common infection leads to high economic (e.g., abortions in sheep) and human (e.g., congenital toxoplasmosis or neurotoxoplasmosis in humans) losses. With one exception (Toxovax for sheep), there are no vaccines to prevent human or animal toxoplasmosis. The paper presents the current state and challenges in the development of a vaccine against toxoplasmosis, designed for farm animals either bred for consumption or commonly kept on farms and involved in parasite transmission. So far, the trials have mostly revolved around conventional vaccines and, compared with the research using laboratory animals (mainly mice), they have not been very numerous. However, the results obtained are promising and could be a good starting point for developing an effective vaccine to prevent toxoplasmosis.

Experimental vaginal infection of goats with semen contaminated with the "CPG" strain of Toxoplasma gondii

The objective was to characterize the transmission of Toxoplasma gondii in goats experimentally infected vaginally with semen contaminated with the CPG strain (genotype III). Ten female goats were randomly allocated into 2 groups (G1 and G2), each with 5 animals, and inseminated during estrus. Goats in G1 were inseminated with semen containing 1 × 10(5) tachyzoites, whereas those in G2 (control) were inseminated with semen free from tachyzoites (insemination = day 0). In G1, seroconversion (indirect immunofluorescence reaction) and DNA (polymerase chain reaction) in the blood was present in 4/5 and 3/5, respectively, from the 7th day. In G2, all goats were negative in all tests. Embryonic reabsorption occurred in 4 of 5 goats from G1 between days 21 and 49. In conclusion, artificial vaginal insemination with semen containing tachyzoites of T. gondii -infected goats and is a potential transmission route of this parasite through semen.

IGM and IGG response to 29-35-kDa Toxoplasma gondii protein fractions in experimentally infected goats

The evolution of the humoral responses of IgG and IgM against 29-35-kDa Toxoplasma gondii fractions from experimentally infected goats were studied and compared by ELISA with the use of whole T. gondii soluble extracts and 29-35-kDa electroeluted proteins as antigens. The IgM response to electroeluted proteins was detected from wk 1 to wk 3 postinfection, showing a similar evolution to that observed when T. gondii crude extracts were used as antigens. These results suggest that this group of proteins could be used for a more specific detection of anti-T. gondii IgM. In the same way, the IgG response was equivalent in both cases, although when 29-35-kDa T. gondii fractions were used as antigens, the level of specific IgGs reached a peak 2 wk before than when T. gondii crude extract was used. The detection by ELISA of anti-T. gondii IgM in goats does not seem to be affected by the presence of specific IgG in serum samples when 29-35-kDa protein fractions were used as antigens.

Toxoplasma gondii infection in adult llamas (Lama glama) and vicunas (Vicugnavicugna) in the Peruvian Andean region

The present study was designed to investigate Toxoplasma gondii infection in adult llamas (Lama glama) and vicunas (Vicugna vicugna) in the Peruvian Andean region, for which to date no information has been available. Serum samples from 43 llamas (L. glama) and 200 vicunas were tested by IFAT detecting titres of 1:50 or higher in 55.8% (33.9-70.9%) and 5.5% (2.8-9.6%), respectively. IFAT titres ranged from 1:50 to 1:6400. In order to avoid cross reactions with closely related coccidian parasites and to confirm the existence of T. gondii specific antibodies, IFAT positive sera from both ruminant species were also analysed by western blot. T. gondii specific antigens were recognised by IFAT positive sera, although different IFAT cut-off points could be selected for llamas (1:200) and vicunas (1:50) meaning seroprevalence of 44.2% (29.1-60.1%) and 5.5% (2.8-9.6%), respectively. Based on the frequency and intensity of tachyzoite antigen recognition, at least three immunodominant antigens with apparent molecular weights of 22-24, 30, and 38-40 kDa were detected, together with other minor protein fractions located in the 18-73 kDa range. This study documents for the first time the presence of T. gondii infection and reports the target T. gondii antigens in adult llamas and vicunas in Peru.

Experimental Corynebacterium pseudotuberculosis primary infection in goats: kinetics of IgG and interferon-gamma production, IgG avidity and antigen recognition by Western blotting

Corynebacterium pseudotuberculosis is the cause of caseous lymphadenitis (CLA) in small ruminants, a chronic granulomatous disease that provokes significant zootechnics losses to ovine and goat breeders in northern Brazil. The present work was conducted to analyse aspects of humoral and cellular immune responses after experimental infection. Eight goats were infected intradermally with a single dose of virulent C. pseudotuberculosis strain and specific IgG, interferon-gamma (IFN-gamma) production as well as IgG avidity and antigens pattern recognition dynamics against an excreted-secreted antigen were recorded during 20 weeks. At the end of the follow-up, animals were slaughtered and necropsied. Although no animals showed apparent clinical signs of infection at the end of the trial, IFN-gamma response, even more so than the humoral response, differentiated animals into two groups of high or medium/low response. The time-course of IFN-gamma production presented a short-lived primary response on day 5 after infection of animals of both groups, and a strong and long lasting secondary response starting on day 16 after infection in the high response group. The indirect ELISA used was able to detect a positive antibody titre between 6 and 11 days after infection in the two groups. IgG avidity index oscillated initially between 15 and 45%, and showed approximately 5% units increment during the 20 follow-up weeks. With only one individual exception, the qualitative antigens pattern recognition showed on day 11 after infection remained constant through the experiment. IgG avidity is highly correlated with IgG production, but could not be related with specific immunodominant bands. Both humoral and cellular responses kinetics presented a similar pattern of activation/deactivation but necropsy results suggested that the IFN-gamma test would be a very specific marker of CLA status.